Supercharged applied ignition internal combustion engine with exhaust-gas turbocharging and method for operating an internal combustion engine of said type

ABSTRACT

A turbocharged internal combustion engine is provided with at least a partially variable valve train on an intake side wherein the intake valves are controlled to optimize the actuation of a second inlet valve in relation to a first inlet valve for different load conditions.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to German Patent Application No.102014210220.0, filed May 28, 2014, and German Patent Application No.102014211835.2, filed Jun. 20, 2014, the entire contents of each ofwhich are hereby incorporated by reference for all purposes.

FIELD

The present disclosure relates to a method and system for controllingintake valve timing of an intake system arranged in an internalcombustion engine with exhaust-gas turbocharging and knock regulator.

BACKGROUND\SUMMARY

Engines may use boosting devices, such as turbochargers, to increaseengine power density. However, engine knock may occur due to increasedcombustion temperatures during boosted conditions. At higher loads, theengine may be more knock-limited which may result in undesired latecombustion phasing.

The engine knock may be addressed by retarding spark timing such asdescribed in US20030131805 A1. In another example, systems with fixedlong intake cams, such as in Atkinson engines and as shown inUS20030131805 A1 as well, may be used for knock control.

The inventors herein have identified potential issues, including issueswith the above approaches to addressing knock limits. For example,significant spark retard can reduce fuel economy and limit maximumtorque. Further, fixed long intake cams may be optimized as a compromisebetween part and full load conditions.

The inventors herein have recognized the above issues and identifiedapproaches to at least partly address the issues. In one exampleapproach, a supercharged engine comprises at least one cylinder headwith at least one cylinder, each cylinder having at least two inletopenings for the supply of charge air via an intake system and at leastone outlet opening for the discharge of the exhaust gases via anexhaust-gas discharge system, at least one throttle flap which isarranged in the intake system and which serves for load control, and atleast one exhaust-gas turbocharger, each exhaust-gas turbochargercomprising a turbine arranged in the exhaust-gas discharge system and acompressor arranged in the intake system. Further, at least two at leastpartially variable valve drives may be provided, the valve drives havingat least two valves which may be movable between a valve closed positionand a valve open position in order to open up and block the at least twoinlet openings of the at least one cylinder, wherein a valve springmeans for may preload the valves in the direction of the valve closedposition. The at least partially variable valve drives may have at leasttwo actuating devices for opening the valves counter to the preloadforce of the valve spring means, each actuating device comprising a camwhich is arranged on a camshaft and which, as the camshaft rotates, maybe brought into engagement with at least one cam follower element,whereby the associated valve is actuated, and the cams of the at leasttwo actuating devices of the at least two at least partially variablevalve drives may be rotatable relative to one another. Further, the atleast two valves may be actuated based on a desired manifold pressureand a corrective factor based on a boost pressure.

In one example, the opening and closing of the inlet valves may beadjusted depending on the load and engine operating conditions. Forexample, closing time of the second inlet valve may be determined bydetermining a base closing time using a present engine speed and apresent desired value for a pressure in an intake system, and correctedfor turbocharging by determining an additive closing time based on boostpressure. In this way, a cam event may be elongated so that part of theair charge may be pushed back into the intake system in order to lowerthe actual compression ratio, which may result in increased efficiency,fuel economy, higher torque, and a combustion process that is lessknock-limited. Further, a correction in the closing time of the inletvalve accounting for a knock regulator output, may be used to retard theclosing of a second inlet valve further. In this way, the method mayreduce or substantially eliminate the need for retarding ignition spark,thus further increasing efficiency. Overall, a turbocharged engine canbe operated with less spark retard from maximum torque.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically depicts an example vehicle system including a camactuation system.

FIG. 2 shows a simplified internal combustion engine with multiplecylinders and an example cam actuation system.

FIG. 3 schematically shows, in a diagram, operating parameters of theinternal combustion engine in the event of a step change in load.

FIG. 4 schematically shows, in a diagram, the determination of theclosing time of the second inlet valve.

FIG. 5 schematically shows, in a diagram, the determination of theclosing time of the second inlet valve including a correction for knock.

FIG. 6 is an example method flowchart for determining intake valvetiming.

DETAILED DESCRIPTION

The present application relates to a supercharged applied-ignitioninternal combustion engine comprising at least one cylinder head with atleast one cylinder, each cylinder having at least two inlet openings forthe supply of charge air via an intake system and at least one outletopening for the discharge of the exhaust gases via an exhaust-gasdischarge system, at least one throttle flap which is arranged in theintake system and which serves for load control, and at least oneexhaust-gas turbocharger is provided, each exhaust-gas turbochargercomprising a turbine arranged in the exhaust-gas discharge system and acompressor arranged in the intake system, and a knock regulator which,as output signal, provides an ignition retardation Δ_(ignition) requiredfor the prevention of knocking.

The present application also relates to a method for operating aninternal combustion engine of said type, with each cylinder comprisingtwo inlet openings for the supply of charge air via an intake system.

An internal combustion engine of the above-stated type is used as adrive for motor vehicles. Within the context of the present application,the expression “internal combustion engine” encompasses Otto-cycleengines and also hybrid internal combustion engines, which utilize ahybrid combustion process, and hybrid drives which comprise not only theinternal combustion engine but also an electric machine which may beconnected in terms of drive to the internal combustion engine and whichreceives power from the internal combustion engine or which, as aswitchable auxiliary drive, additionally outputs power.

Internal combustion engines have a cylinder block and at least onecylinder head which are connected to one another to form the at leastone cylinder or combustion chamber. To hold the pistons or the cylinderliners, the cylinder block has a corresponding number of cylinder bores.The cylinder head conventionally serves to hold the valve drive. Tocontrol the charge exchange, an internal combustion engine requirescontrol elements and actuating devices for actuating the controlelements. During the charge exchange, the combustion gases aredischarged via the outlet openings and the charging of the combustionchamber with charge air takes place via the inlet openings. To controlthe charge exchange, in four-stroke engines, use is made almostexclusively of lifting valves as control elements, which lifting valvesperform an oscillating lifting movement during the operation of theinternal combustion engine and which lifting valves open and close theinlet and outlet openings in this way. The actuating device required forthe movement of a valve, including the valve itself, is referred to asthe valve drive.

An actuating device comprises a camshaft on which at least one cam isarranged. A basic distinction is made between an underlying camshaft andan overhead camshaft. This relates to the parting plane between thecylinder head and cylinder block. If the camshaft is arranged above saidparting plane, it is an overhead camshaft, otherwise it is an underlyingcamshaft.

Overhead camshafts are likewise mounted in the cylinder head, wherein avalve drive with overhead camshaft may, as a further valve drivecomponent, have a rocker lever, a finger-type rocker, a tilting leverand/or a tappet. Said cam follower elements are situated in the forceflow between cam and valve.

It is the object of the valve drive to open and close the inlet andoutlet openings of a cylinder at the correct times, with a fast openingof the greatest possible flow cross sections being sought in order tokeep the throttling losses in the inflowing and outflowing gas flows lowand in order to ensure the best possible charging of the cylinder, and acomplete discharge of the exhaust gases. According to some approaches,therefore, a cylinder is also often and increasingly provided with twoor more inlet and outlet openings.

In the development of internal combustion engines, it is a basic aim tominimize fuel consumption, wherein the emphasis in the efforts beingmade is on obtaining an improved overall efficiency.

Fuel consumption and thus efficiency pose a problem, for example in thecase of Otto-cycle engines, that is to say in the case ofapplied-ignition internal combustion engines. The reason for this liesin the principle of the operating process of the Otto-cycle engine. Loadcontrol is generally carried out by means of a throttle flap provided inthe intake system. By adjusting the throttle flap, the pressure of theinducted air downstream of the throttle flap may be reduced to a greateror lesser extent. The further the throttle flap is closed, that is tosay the more said throttle flap blocks the intake system, the higher isthe pressure loss of the inducted air across the throttle flap, and thelower is the pressure of the inducted air downstream of the throttleflap and upstream of the inlet into the at least one cylinder, that isto say combustion chamber. For a constant combustion chamber volume, itis possible in this way for the air mass, that is to say the quantity,to be set by means of the pressure of the inducted air. This alsoexplains why quantity regulation has proven to be disadvantageousspecifically in part-load operation, because low loads require a highdegree of throttling and a pressure reduction in the intake system, as aresult of which the charge exchange losses increase with decreasing loadand increasing throttling.

To reduce the described losses, various strategies for dethrottling anOtto-cycle engine have been developed.

One approach to a solution for dethrottling the Otto-cycle engine is forexample an Otto-cycle engine operating process with direct injection.The direct injection of the fuel is a suitable means for realizing astratified combustion chamber charge. The direct injection of the fuelinto the combustion chamber thus permits quality regulation in theOtto-cycle engine, within certain limits. The mixture formation takesplace by direct injection of the fuel into the cylinder or into the airsituated in the cylinder, and not by external mixture formation, inwhich the fuel is introduced into the inducted air in the intake system.

A further approach to a solution for optimizing the combustion processof an Otto-cycle engine consists in the use of an at least partiallyvariable valve drive. By contrast to conventional valve drives, in whichboth the lift of the valves and the timing are invariable, theseparameters which have an influence on the combustion process, and thuson fuel consumption, may be varied to a greater or lesser extent bymeans of variable valve drives. If the valve drive is partially variableor switchable and, for example, the closing time of the inlet valve andthe inlet valve lift may be varied, this alone makes throttling-free andthus loss-free load control possible. The mixture mass or charge airmass which flows into the combustion chamber during the intake processis then controlled not by means of a throttle flap but rather by meansof the inlet valve lift and the opening duration of the inlet valve.Fully variable valve drives are very expensive, for which reason use isoften made of partially variable or switchable valve drives. Within thecontext of the present application, switchable valve drives are regardedas partially variable valve drives.

In this connection, it must also be taken into consideration that theefficiency η of the Otto-cycle engine at least approximately correlateswith the compression ratio ε. That is to say, the efficiency η increaseswith the compression ratio ε, is generally higher in the presence of arelatively high compression ratio, and is generally lower in thepresence of a relatively low compression ratio.

With regard to efficiency, the cylinders would thus may be provided withthe highest possible compression ratio. The compression ratio howevercannot be increased to an arbitrary extent because, with increasingcompression ratio, the knocking tendency, that is to say the tendencyfor auto-ignition of mixture components, increases. Modern Otto-cycleengines generally have compression ratios of approximately 8 to 10, witha compression ratio of approximately 15 promising the best efficiency.In this way, although efficiency is limited, the required resistance toknocking, for example at high loads, is ensured. According to someapproaches, the knocking tendency is also counteracted by virtue of theignition being retarded as required, whereby the combustion center ofgravity is retarded and the combustion pressure and combustiontemperature decrease. For this purpose, modern Otto-cycle engines areequipped with a knock regulator which, as output signal, provides anignition retardation required for the prevention of knocking. Theignition retardation however has an adverse effect on the efficiency.

The internal combustion engine to which the present application relateshas a knock regulator of said type, and also at least one exhaust-gasturbocharger. The advantage of an exhaust-gas turbocharger in relationto a mechanical charger is that no mechanical connection fortransmitting power exists or is required between the charger andinternal combustion engine. While a mechanical charger extracts theenergy required for driving it entirely from the internal combustionengine, and thereby reduces the output power and consequently adverselyaffects the efficiency, the exhaust-gas turbocharger utilizes theexhaust-gas energy of the hot exhaust gases.

An exhaust-gas turbocharger comprises a compressor arranged in theintake system and a turbine arranged in the exhaust-gas dischargesystem, which compressor and turbine are arranged on the same shaft. Thehot exhaust-gas flow is supplied to the turbine and expands in saidturbine with a release of energy, as a result of which the shaft is setin rotation. The energy supplied by the exhaust-gas flow to the turbineand ultimately to the shaft is used for driving the compressor which islikewise arranged on the shaft. The compressor delivers and compressesthe charge air supplied to it, as a result of which supercharging of theat least one cylinder is obtained. A charge-air cooling arrangement maybe provided, by means of which the compressed charge air is cooledbefore it enters the cylinder.

Supercharging serves primarily to increase the power of the internalcombustion engine. Here, the air required for the combustion process iscompressed, as a result of which a greater air mass may be supplied toeach cylinder per working cycle. In this way, the fuel mass andtherefore the mean pressure may be increased. Supercharging is asuitable means for increasing the power of an internal combustion enginewhile maintaining an unchanged swept volume, or for reducing the sweptvolume while maintaining the same power. In any case, superchargingleads to an increase in volumetric power output and an improvedpower-to-weight ratio. For the same vehicle boundary conditions, it isthus possible to shift the load collective toward higher loads, at whichthe specific fuel consumption is lower and the efficiency is higher.

Against the background of that stated above, it is an object of thepresent application to provide a supercharged applied-ignition internalcombustion engine according to the preamble of claim 1, which isoptimized with regard to operating behavior, for example with regard tofuel consumption and efficiency.

It is a further sub-object to specify a method for operating an internalcombustion engine of said type, wherein each cylinder comprises twoinlet openings for the supply of charge air via an intake system, andeach piston belonging to a cylinder oscillates between a top dead centerand a bottom dead center.

The first sub-object is achieved by means of a superchargedapplied-ignition internal combustion engine comprising at least onecylinder head with at least one cylinder, each cylinder comprising atleast two inlet openings for the supply of charge air via an intakesystem and at least one outlet opening for the discharge of the exhaustgases via an exhaust-gas discharge system, at least one throttle flapwhich is arranged in the intake system and which serves for loadcontrol, and at least one exhaust-gas turbocharger is provided, eachexhaust-gas turbocharger comprising a turbine arranged in theexhaust-gas discharge system and a compressor arranged in the intakesystem, and a knock regulator which, as output signal, provides anignition retardation Δ_(ignition) required for the prevention ofknocking, which internal combustion engine is distinguished by the factthat at least two at least partially variable valve drives are provided,the valve drives comprising at least two valves which are movablebetween a valve closed position and a valve open position in order toopen up and block the at least two inlet openings of the at least onecylinder, having valve spring means for preloading the valves in thedirection of the valve closed position, and having at least twoactuating devices for opening the valves counter to the preload force ofthe valve spring means, each actuating device comprising a cam which isarranged on a camshaft and which, as the camshaft rotates, is broughtinto engagement with at least one cam follower element, whereby theassociated valve is actuated, and the cams of the at least two actuatingdevices of the at least two at least partially variable valve drivesbeing rotatable relative to one another.

According to the present application, the timings of the inlet valves ofa cylinder may be varied.

In the present case, the cams of the valve actuating devices whichbelong to the inlet valves of a cylinder, may be rotated relative to oneanother, such that the inlet valves belonging to a cylinder may not onlybe actuated synchronously, that is to say opened and closedsimultaneously. Rather, the cams, belonging to the inlet valves or inletopenings of a cylinder, may be rotated relative to one another such thata first inlet valve is actuated earlier than a second inlet valve. Thetimings of the inlet valves then have an offset, hereinafter alsoreferred to as control offset Δ. This control offset makes it possibleto vary the inlet-side opening duration, wherein the opening durationextends from the opening of the first inlet valve to the closing of thesecond inlet valve.

The variable valve drives on the inlet side permit an adaptation of thetimings of the inlet valves to the present operating state of theinternal combustion engine, for example an adaptation to the presentload and to the present knocking tendency. In this connection, theadaptation of the inlet-side opening duration to the present operatingstate of the internal combustion engine is of particular interest.

With regard to low fuel consumption, a large inlet-side openingduration, that is to say an inlet-side opening duration which is as longas possible, may be preferable in part-load operation in the presence oflow loads. In this context, a high compression ratio is additionallyconducive to reducing fuel consumption

In the presence of increased load, it is then the case in part-loadoperation up to medium loads that a shorter inlet-side opening durationis desired in order to ensure the best possible charging of thecylinder. The background to this measure is the increase of the torqueat medium loads, that is to say the improvement of the torquecharacteristic of the internal combustion engine.

Toward higher loads, the operation of the internal combustion engine isprogressively limited owing to the fact that knocking should be reliablyprevented under all circumstances. According to some approaches,knocking is counteracted by virtue of the ignition time being retarded.In this case, losses in efficiency are accepted.

By contrast, according to the present application, the effectivecompression ratio ε_(eff) may be lowered by lengthening the inlet-sideopening duration or through retarded closing of one inlet valve, forexample of the second inlet valve, wherein, with an inlet still open, apart of the cylinder fresh charge is displaced into the intake systemagain during the compression stroke. A high geometric compression ratioε_(geo), which is basically to be regarded as advantageous and which, atrelatively low loads, is highly conducive to improving efficiency, mayin this way be mitigated at relatively high loads

According to the present application, when there is a risk of knocking,at least the second inlet valve is closed later and after bottom deadcenter, wherein a closing time retardation Δt_(intake,closing,knock) bywhich the closure of the second inlet valve is to be retarded isdetermined using a present engine speed n_(mot) and an ignitionretardation output by the knock regulator. The retardation of theignition time, such as is required according to some approaches, isomitted, along with the associated efficiency losses. It is however atleast the case that the required ignition retardation may be reduced.

The internal combustion engine according to the present applicationachieves the first object on which the present application is based,specifically that of providing an internal combustion engine which isoptimized with regard to operating behavior, for example with regard tofuel consumption and efficiency.

According to the present application, the cams of the inlet valves of acylinder are rotatable relative to one another. In this case, thetimings of the valves may be shifted relative to one another whilemaintaining the valve opening duration of each valve, such that theinlet-side opening duration of the associated cylinder may be lengthenedor shortened. The valve overlap of the valves may be varied.

This adjustment possibility requires at least one rotatable cam. In afirst alternative, a cam which is designed to be adjustable is rotatedrelative to the crankshaft, whereas the at least one other cam isdesigned as an immovable, static cam. In a second alternative, the atleast two cams are designed as adjustable cams which are rotatablerelative to one another and relative to the crankshaft.

Further advantageous embodiments of the internal combustion engineaccording to the present application will be explained in conjunctionwith the subclaims.

Embodiments of the internal combustion engine are advantageous in whichthe cams are arranged on an at least two-part camshaft which comprisesat least two camshaft sections that are rotatable relative to oneanother, wherein at least one cam is arranged on a first camshaftsection and at least one cam is arranged on a second camshaft section.An example of a camshaft of the above type is described in Germanlaid-open specification DE 10 2010 008 958 A1.

Here, embodiments of the internal combustion engine are advantageous inwhich the at least two-part camshaft comprises, as first camshaftsection, a hollow shaft and, as second camshaft section, a shaftarranged rotatably in the hollow shaft.

In the case of internal combustion engines with a crankshaft which is atleast connectable in terms of drive to the camshaft, embodiments arealso advantageous in which the cams are rotatable relative to thecrankshaft, for example with one another and relative to the crankshaft.

In this case, the cams may be rotated individually or, as in the case ofa camshaft adjuster, rotated conjointly and similarly relative to thecrankshaft. In the latter variant, the timings of the associated valvesare jointly retarded or advanced while maintaining the respective valveopening duration.

Embodiments of the internal combustion engine are advantageous in whichthe cams have the same contour.

Embodiments of the internal combustion engine are advantageous in whicheach cylinder is equipped with a direct-injection means for fuel supplypurposes. The direct injection of the fuel into the cylinder is asuitable means for reducing the knocking tendency of the Otto-cycleengine, and is thus a measure for improving efficiency.

Embodiments of the internal combustion engine are advantageous in whicheach cylinder has a geometric compression ratio ε_(geo)≧11.

Embodiments of the internal combustion engine are advantageous in whicheach cylinder has a geometric compression ratio ε_(geo)≧11.5.

Embodiments of the internal combustion engine are advantageous in whicheach cylinder has a geometric compression ratio ε_(geo)≧12.

The higher the compression ratio, the higher the efficiency, and thusthe lower the fuel consumption. However, under some circumstances,higher geometric compression ratios require greater variability of thevalve drive in order to be able to lower the effective compression ratioto a more pronounced or adequate extent.

Embodiments of the internal combustion engine are advantageous in whichthe actuating devices of the inlet valves are hydraulically adjustableactuating devices.

In the case of internal combustion engines comprising at least twocylinders, embodiments may be advantageous in which at least twocylinders are configured in such a way that they form at least twogroups with in each case at least one cylinder, wherein the at least onecylinder of a first group is a cylinder which is in operation even inthe event of a partial deactivation of the internal combustion engine,and the at least one cylinder of a second group is formed as a cylinderwhich may be switched in a load-dependent manner.

The cylinder deactivation, that is to say the deactivation of individualcylinders in certain load ranges, offers a further option fordethrottling the Otto-cycle engine. The efficiency of the Otto-cycleengine in part-load operation may be improved, that is to say increased,by means of a partial deactivation because the deactivation of onecylinder of a multi-cylinder internal combustion engine increases theload on the other cylinders, which remain in operation, if the enginepower remains constant, such that the throttle flap may or must beopened further in order to introduce a greater air mass into saidcylinders, whereby dethrottling of the internal combustion engine isattained overall. Furthermore, during the partial deactivation, that isto say at part load, the cylinders which are permanently in operationoften operate in the region of higher loads, at which the specific fuelconsumption is lower. The load collective is shifted toward higherloads.

The cylinders which remain in operation during the partial deactivationfurthermore exhibit improved mixture formation owing to the greater airmass supplied. Further advantages with regard to efficiency are attainedin that a deactivated cylinder, owing to the absence of combustion, maynot generate any wall heat losses owing to heat transfer from thecombustion gases to the combustion chamber walls.

The second sub-object on which the present application is based,specifically that of specifying a method for operating an internalcombustion engine of a type described above, in which each cylinder hastwo inlet openings for the supply of charge air via an intake system andeach piston belonging to a cylinder oscillates between a top dead centerand a bottom dead center, is achieved by means of a method wherein, whenthere is a risk of knocking, at least the second inlet valve is closedlater and after bottom dead center.

That which has been stated in connection with the internal combustionengine according to the present application likewise applies to themethod according to the present application.

Method variants are advantageous in which a closing time retardationΔ_(tintake,closing,knock) by which the closure of the second inlet valveis to be retarded is determined using a present engine speed n_(mot) andan ignition retardation Δignition output by the knock regulator.

Method variants may be advantageous in which, proceeding from arelatively low load at which the cams belonging to the two inletopenings of each cylinder are rotationally offset relative to oneanother such that a first inlet valve may be actuated earlier than asecond inlet valve, thus forming a control offset Δ, in the presence ofan abruptly increased load demand the throttle flap is opened further,the control offset Δ is reduced by virtue of the second inlet valvebeing actuated earlier, and the control offset Δ is increased again, ina manner dependent on a charge pressure generated in the intake systemby exhaust-gas turbocharging, by virtue of the second inlet valve beingactuated later, and when the at least one exhaust-gas turbochargergenerates charge pressure.

If the internal combustion engine is used for example as a drive for amotor vehicle, an increased load may be demanded by actuating theaccelerator pedal. Here, it may be the case for example in anacceleration situation that the load also increases abruptly, that is tosay a step change in load is realized. The subsequent transientoperation of the internal combustion engine is determined primarily bydifferent response behaviors of the individual components that serve forsetting the operating parameters. Whereas, in the presence of anabruptly increased load demand, the throttle flap may be opened furtherreadily, that is to say virtually without a delay, the exhaust-gasturbocharger requires a certain amount of time to be able to generate,that is to say provide, the required charge pressure.

According to the present application, in the presence of an abruptlyincreased load demand, the throttle flap is opened further and thecontrol offset Δ of the inlet valves is reduced by virtue of the secondinlet valve being actuated earlier than before the load demand. In thiscase, it is assumed that, before a relatively high load is demanded,that is to say in the presence of relatively low load, the first inletvalve is actuated earlier than the second inlet valve, that is to say acontrol offset Δ for realizing a lengthened inlet-side opening durationis present.

This control offset Δ is now initially reduced or minimized in thepresence of an abruptly increased load demand, whereby the inlet-sideopening duration is shortened. A shorter inlet-side opening duration isintended to ensure the best possible charging of the at least onecylinder, and thus a high torque availability at the start of theacceleration.

During the further process, when the at least one exhaust-gasturbocharger responds and generates a charge pressure in the intakesystem, the control offset Δ is then increased again, that is to say theinlet-side opening duration is lengthened again, in a manner dependenton said charge pressure. This approach makes allowance for the fact thatthe knocking tendency likewise increases with increasing chargepressure. Knocking is prevented according to the present application inthat the effective compression ratio ε_(eff) is lowered by way of alengthening of the inlet-side opening duration, specifically by way of aretarded closure of the second inlet valve. Here, with the inlet stillopen, a part of the cylinder fresh charge, that is to say charge air, isdisplaced into the intake system again. The higher the charge pressureis, the later the second inlet valve is closed, or the later the secondinlet valve should be closed.

Method variants may be advantageous in which the throttle flap is fullyopened in the presence of an abruptly increased load demand.

Method variants may be advantageous in which the control offset Δ isminimized during the course of the reduction.

Method variants may be advantageous in which the control offset Δ isadditionally reduced by virtue of the first inlet valve being actuatedlater.

For the operation of a supercharged applied-ignition internal combustionengine, in which each piston belonging to a cylinder oscillates betweena top dead center and a bottom dead center, method variants may beadvantageous which are distinguished by the fact that, in the presenceof the relatively low load before the increased load demand, the firstinlet valve is closed before bottom dead center and the second inletvalve is closed after bottom dead center.

In this connection, method variants may be advantageous in which thecontrol offset Δ is reduced by virtue of the second inlet valve beingclosed before bottom dead center.

Method variants may be advantageous in which a closing timet_(intake,closing,2) at which the second inlet valve is closed iscalculated in that,

in a first method step, a base closing time t_(intake,closing,base,2) isdetermined using a present engine speed n_(mot) and a present desiredvalue for the pressure p_(intake,des) in the intake system, in a secondmethod step, an additive closing time Δt_(intake,closing,2) isdetermined using a present engine speed n_(mot) and a present actualvalue for the pressure p_(intake) in the intake system, and in a thirdmethod step, the closing time t_(intake,closing,2) is calculated byadding the base closing time and the additive closing time, wheret_(intake,closing,2)=t_(intake,closing,base,2)+Δt_(intake,closing,2).

In the present case, a base closing time t_(intake,closing,base,2) isinitially determined, wherein the charge pressure and thus thesupercharging may be ignored, that is to say disregarded. The chargepressure and thus the supercharging are first allowed for by way of asecond additive component Δt_(intake,closing,2).

A closing time retardation Δ_(tintake,closing,knock) which is determinedaccording to the present application for the purposes of preventingknocking and by which the closure of the second inlet valve is to beretarded must then if appropriate additionally be taken intoconsideration, that is to say added, in the calculation of the closingtime t_(intake,closing,2).

In this connection, method variants may be advantageous in which, forthe first method step, an ambient pressure p_(atm) is predefined whichis used as a maximum admissible desired value for the pressurep_(intake,des) in the intake system and by means of which the desiredvalue for the pressure p_(intake,des) in the intake system in thedetermination of the base closing time is limited.

To ensure that the charge pressure and thus the supercharging areactually disregarded in the first method step, a maximum admissibledesired value is predefined, specifically the ambient pressure p_(atm),which may be for example 1013 hPa. In this case, the superchargedinternal combustion engine is considered as a naturally aspiratedengine.

In this connection, method variants may be likewise advantageous inwhich, for the second method step, an ambient pressure p_(atm) ispredefined which is subtracted from the present actual value for thepressure p_(intake) in the intake system in order to determine a chargepressure difference Δp_(charge), the additive closing timeΔt_(intake,closing,2) being determined using said charge pressuredifference Δp_(charge) if Δp_(charge)>0.

To ensure that only the effect generated by the supercharging or thecharge pressure is taken into consideration in the second method step,the ambient pressure p_(atm) is subtracted from the actual pressurep_(intake) in the intake system, thus forming a charge pressuredifference Δp_(charge). The second method step then provides an additiveclosing time Δt_(intake,closing,2) only if Δp_(charge)>0, that is to sayif the at least one exhaust-gas turbocharger responds and generates acharge pressure in the intake system.

Referring specifically to FIG. 1, it includes a schematic diagramshowing one cylinder of multi-cylinder internal combustion engine 100.Engine 100 may be controlled at least partially by a control systemincluding controller 120 and by input from a vehicle operator 132 via aninput device 130. In this example, input device 130 includes anaccelerator pedal and a pedal position sensor 134 for generating aproportional pedal position signal PP.

Combustion cylinder 30 of engine 100 may include combustion cylinderwalls 32 with piston 36 positioned therein. Piston 36 may be coupled tocrankshaft 40 so that reciprocating motion of the piston is translatedinto rotational motion of the crankshaft. Crankshaft 40 may be coupledto at least one drive wheel of a vehicle via an intermediatetransmission system. Further, a starter motor may be coupled tocrankshaft 40 via a flywheel to enable a starting operation of engine100.

Combustion cylinder 30 may receive intake air from intake manifold 44via intake passage 42 and may exhaust combustion gases via exhaustpassage 48. Intake manifold 44 and exhaust passage 48 can selectivelycommunicate with combustion cylinder 30 via respective intake valve 52and exhaust valve 54. In some embodiments, combustion cylinder 30 mayinclude two or more intake valves and/or two or more exhaust valves suchas shown in FIG. 2 and further elaborated below.

In this example, intake valve 52 and exhaust valve 54 may be controlledby cam actuation via respective cam actuation systems 51 and 53. Camactuation systems 51 and 53 may each include one or more cams and mayutilize one or more of cam profile switching (CPS), cam-in-cam (CiC),variable cam timing (VCT), variable valve timing (VVT) and/or variablevalve lift (VVL) systems that may be operated by controller 120 to varyvalve operation. The position of intake valve 52 and exhaust valve 54may be determined by position sensors 55 and 57, respectively or viacamshaft sensors.

Combustion cylinder 30 includes a fuel injector 66 arranged in intakepassage 42 in a configuration that provides what is known as portinjection of fuel into the intake port upstream of combustion cylinder30. Fuel injector 66 injects fuel therein in proportion to the pulsewidth of signal FPW received from controller 120 via electronic driver68. Alternatively or additionally, in some embodiments the fuel injectormay be mounted on the side of the combustion cylinder or in the top ofthe combustion cylinder, for example, to provide what is known as directinjection of fuel into combustion cylinder 30. Fuel may be delivered tofuel injector 66 by a fuel delivery system (not shown) including a fueltank, a fuel pump, and a fuel rail.

Intake passage 42 may include a throttle 62 having a throttle plate 64.In this particular example, the position of throttle plate 64 may bevaried by controller 120 via a signal provided to an electric motor oractuator included with throttle 62, a configuration that may be referredto as electronic throttle control (ETC). In this manner, throttle 62 maybe operated to vary the intake air provided to combustion cylinder 30among other engine combustion cylinders. Intake passage 42 may include amass air flow sensor 121 and a manifold air pressure sensor 122 forproviding respective signals MAF and MAP to controller 120.

Ignition system 88 can provide an ignition spark to combustion chamber30 via spark plug 92 in response to spark advance signal SA fromcontroller 120, under select operating modes. Though spark ignitioncomponents are shown, in some embodiments, combustion chamber 30 or oneor more other combustion chambers of engine 100 may be operated in acompression ignition mode, with or without an ignition spark.

Exhaust gas sensor 126 is shown coupled to exhaust passage 48 upstreamof catalytic converter 70. Sensor 126 may be any suitable sensor forproviding an indication of exhaust gas air/fuel ratio such as a linearoxygen sensor or UEGO (universal or wide-range exhaust gas oxygen), atwo-state oxygen sensor or EGO, a HEGO (heated EGO), a NO_(x), HC, or COsensor. The exhaust system may include light-off catalysts and underbodycatalysts, as well as exhaust manifold, upstream and/or downstreamair-fuel ratio sensors. Catalytic converter 70 can include multiplecatalyst bricks, in one example. In another example, multiple emissioncontrol devices, each with multiple bricks, can be used. Catalyticconverter 70 can be a three-way type catalyst in one example.

Controller 120 is shown in FIG. 1 as a microcomputer, includingmicroprocessor unit 102, input/output ports 104, an electronic storagemedium for executable programs and calibration values shown as read onlymemory chip 106 in this particular example, random access memory 108,keep alive memory 110, and a data bus. The controller 120 may receivevarious signals and information from sensors coupled to engine 100, inaddition to those signals previously discussed, including measurement ofinducted mass air flow (MAF) from mass air flow sensor 120; enginecoolant temperature (ECT) from temperature sensor 112 coupled to coolingsleeve 114; a profile ignition pickup signal (PIP) from Hall effectsensor 118 (or other type) coupled to crankshaft 40; throttle position(TP) from a throttle position sensor; and absolute manifold pressuresignal, MAP, from sensor 122. Storage medium read-only memory 106 can beprogrammed with computer readable data representing instructionsexecutable by processor 102 for performing the methods described belowas well as variations thereof. Controller 120 may also include a knockregulator to monitor knock based on various signals from sensors, suchas in-cylinder pressure sensors, ambient temperature sensors, and/or aircharge temperature sensors, for example.

Engine 100 may further include a compression device such as aturbocharger 190 or supercharger including at least a compressor 94arranged along intake manifold 44. For a turbocharger, compressor 94 maybe at least partially driven by a turbine 94 (e.g., via a shaft)arranged along exhaust passage 48. For a supercharger, compressor 162may be at least partially driven by the engine and/or an electricmachine, and may not include a turbine. Thus, the amount of compression(e.g., boost) provided to one or more cylinders of the engine via aturbocharger or supercharger may be varied by controller 120. Further, asensor 123 may be disposed in intake manifold 44 for providing a BOOSTsignal to controller 120.

As mentioned previously, intake valve 52 and exhaust valve 54 may becontrolled by cam actuation. As such, an example cam actuation system200 is shown in FIG. 2, which may be used with engine 10 of FIG. 1,where engine 10 is also simply outlined in FIG. 2. Cam actuation system200 may include a variable cam timing (VCT) system 202 and a cam profileswitching (CPS) system 204, and/or other similar cam systems.Furthermore, a turbocharger 206, a catalyst 208, and a cylinder head 210with a plurality of cylinders 212 may be present.

Engine 10 is shown having an intake manifold 214 configured to supplyintake air and/or fuel to the cylinders 212 and an integrated exhaustmanifold 216 configured to exhaust the combustion products from thecylinders 212. Exhaust manifold 216 may include an outlet 248 to coupleto turbocharger 206 while an exhaust passage 246 may couple turbocharger206 to catalyst 208. While in the embodiment depicted in FIG. 2, intakemanifold 214 is separate from cylinder head 210 while exhaust manifold216 is integrated in cylinder head 210, in other embodiments, intakemanifold 214 may be integrated and/or exhaust manifold 216 may beseparate from cylinder head 210.

Cylinder head 210 includes four cylinders, labeled C1-C4. Cylinders 212may each include a spark plug and a fuel injector for delivering fueldirectly to the combustion chamber, as described above in FIG. 1.However, in alternate embodiments, each cylinder may not include a sparkplug and/or direct fuel injector. Cylinders may each be serviced by oneor more valves. In the present example, cylinders 212 each include twointake (inlet) valves and two exhaust valves. Each intake and exhaustvalve is configured to open and close an intake port and exhaust port,respectively. The intake valves are labeled I1-I8 and the exhaust valvesare labeled E1-E8. Cylinder C1 includes intake valves I1 and I2 andexhaust valves E1 and E2; cylinder C2 includes intake valves 13 and 14and exhaust valves E3 and E4; cylinder C3 includes intake valves I5 andI6 and exhaust valves E5 and E6; and cylinder C4 includes intake valvesI7 and I8 and exhaust valves E7 and E8. Each exhaust port of eachcylinder may be of equal diameter. However, in some embodiments, some ofthe exhaust ports may be of different diameter.

Each intake valve is moveable between an open position allowing intakeair into a respective cylinder and a closed position substantiallyblocking intake air from the respective cylinder. Further, FIG. 2 showshow intake valves I1-I8 may be actuated by a common intake camshaft 218.Intake camshaft 218 includes a plurality of intake cams configured tocontrol the opening and closing of the intake valves. Intake camshaft218 may be a cam-in-cam which may comprise two camshaft sections, forexample, where a first cam is arranged on the first camshaft section,and a second cam is arranged on a second camshaft section. One camshaftsection may be an outer camshaft section and may be hollow, having theother, inner camshaft section arranged inside of the first section in arotatable fashion. The camshaft sections may be rotatable relative toeach other, and therefore the first and second cams arranged on therespective camshaft sections are rotatable relative to each other. Eachintake valve may be controlled by first intake cams 220 and secondintake cams 222. Further, in some embodiments, one or more additionalintake cams may be included to control the intake valves. In the presentexample, first intake cams 220 have a first cam lobe profile for openingthe intake valves for a first intake duration. Further, in the presentexample, second intake cams 222 have a second cam lobe profile foropening the intake valve for a second intake duration. In one example,the time between the opening of first intake valve and the closing ofthe second intake valve (control offset A) may be shortened orlengthened depending on engine operating conditions and load asdiscussed further below and shown in FIGS. 3-6. The control offset Δ maybe adjusted by advancing the actuation of a first intake valve of acylinder and/or retarding a second intake valve of the same cylinder.Further, the timing of the intake valves may be corrected forturbocharging and knock effects as elaborated on in FIGS. 4-6. Thesecond intake duration may be a shorter intake duration (shorter thanthe first intake duration), the second intake duration may be a longerintake duration (longer than the first duration), or the first andsecond duration may be equal. Additionally, intake camshaft 218 mayinclude one or more null cam lobes. Null cam lobes may be configured tomaintain respective intake valves in the closed position.

Each exhaust valve is moveable between an open position allowing exhaustgas out of a respective cylinder of the cylinders 212 and a closedposition substantially retaining gas within the respective cylinder.Further, FIG. 2 shows how exhaust valves E1-E8 may be actuated by acommon exhaust camshaft 224. Exhaust camshaft 224 includes a pluralityof exhaust cams configured to control the opening and closing of theexhaust valves. Each exhaust valve may be controlled by first exhaustcams 226 and second exhaust cams 228. Further, in some embodiments, oneor more additional exhaust cams may be included to control the exhaustvalves.

An integrated exhaust manifold 216, included within the engine cylinderhead, may also be provided and configured with one or multiple outletsto selectively direct exhaust gas to various exhaust components.Integrated exhaust manifold 216 may include multiple separate exhaustmanifolds, each having one outlet. Furthermore, the separate exhaustmanifolds may be included in a common casting in cylinder head 210. Inthis present example, integrated exhaust manifold 216 includes thesingle outlet 248 coupled to turbocharger 206.

Additional elements not shown may further include push rods, rockerarms, hydraulic lasher adjusters, tappets, etc. Such devices andfeatures may control actuation of the intake valves and the exhaustvalves by converting rotational motion of the cams into translationalmotion of the valves. In other examples, the valves can be actuated viaadditional cam lobe profiles on the camshafts, where the cam lobeprofiles between the different valves may provide varying cam liftheight, cam duration, and/or cam timing. However, alternative camshaft(overhead and/or pushrod) arrangements could be used, if desired.Further, in some examples, cylinders 212 may each have only one exhaustvalve, or more than two intake and/or exhaust valves. In still otherexamples, exhaust valves and intake valves may be actuated by a commoncamshaft. However, in an alternate embodiment, at least one of theintake valves and/or exhaust valves may be actuated by its ownindependent camshaft or other device.

As described above, FIG. 2 shows a non-limiting example of cam actuationsystem and associated intake and exhaust systems. It should beunderstood that in some embodiments, the engine may have more or fewercombustion cylinders, control valves, throttles, and compressiondevices, among others. Example engines may have cylinders arranged in a“V” configuration. Further, a first camshaft may control the intakevalves for a first group or bank of cylinders and a second camshaft maycontrol the intake valves for a second group of cylinders. In thismanner, a single cam actuation system may be used to control valveoperation of a group of cylinders, or separate cam actuation systems maybe used.

FIG. 3 schematically shows, in a diagram, operating parameters of theinternal combustion engine in the event of a step change in load. In thepresent case, the internal combustion engine is used as a drive for amotor vehicle and has two inlet openings per cylinder.

In the illustration, on the left-hand ordinate, the position of theaccelerator pedal [%] is plotted as curve A, the position of thethrottle flap [%] is plotted as curve B, the torque [%] is plotted ascurve C, and the closing times t_(closing,1) and t_(closing,2) of thefirst and second inlet valves in degrees crank angle after bottom deadcenter of the charge exchange [° CAaBDC] are plotted as curve E1 and E2respectively. On the right-hand ordinate, the pressure p_(intake) in theintake system or the charge pressure p_(charge) in [hPa] is plotted ascurve D. The time t in seconds is plotted on the abscissa.

The load demand is abruptly increased by actuation of the acceleratorpedal. The throttle flap is opened, specifically to its full extent,virtually without a delay.

Triggered by the abruptly increased load demand, the control offset Δ ofthe inlet valves is reduced by virtue of the second inlet valve beingclosed earlier. As shown in FIG. 3, in the presence of low load beforethe load increase, the first inlet valve is closed earlier than thesecond inlet valve. At that time t, the closing times have a largecontrol offset Δ in order to realize a long inlet-side opening duration.This may have advantages in the presence of low load.

In the present case, the control offset Δ is minimized in the presenceof increased load demand, whereby the inlet-side opening duration isshortened. A shorter inlet-side opening duration is intended to ensurethe best possible charging of the at least one cylinder, and thus a hightorque availability at the start of the acceleration.

When the exhaust-gas turbocharging arrangement responds and generatescharge pressure p_(charge) the control offset Δ is then increased again,that is to say the inlet-side opening duration is lengthened again,specifically by retarded closure of the second inlet valve, in a mannerdependent on said charge pressure p_(charge). In this way, the effectivecompression ratio ε_(eff) is lowered, and knocking may be prevented.With the second inlet valve open, a part of the charge air is displacedinto the intake system again. The higher the charge pressure, the laterthe second inlet valve is closed.

The timings of the inlet valves of a cylinder may be varied. FIG. 4schematically shows, in a diagram, the determination of the closing timet_(intake,closing,2) of the second inlet valve.

In a first method step, using the engine speed n_(mot) of the internalcombustion engine and a desired value for the pressure p_(intake,des) inthe intake system, a base closing time t_(intake,closing,base,2) isdetermined (upper branch). In this case, the ambient pressure p_(atm) ispredefined as the maximum admissible desired value for the pressurep_(intake,des) in the intake system. Supercharging effects, if present,may be thus disregarded.

In a second method step, using the engine speed n_(mot) and the actualpressure p_(intake) in the intake system, an additive closing timeΔt_(intake,closing,2) is determined, and thus allowance is made for thesupercharging (lower branch).

Here, a charge pressure difference Δp_(charge) is determined by virtueof the ambient pressure p_(atm) being subtracted from the actualpressure p_(intake) in the intake system. The additive closing timeΔt_(intake,closing,2) is then determined using said charge pressuredifference Δp_(charge), but only if Δp_(charge)>0. The second methodstep provides an additive closing time Δt_(intake,closing,2) only if theexhaust-gas turbocharging arrangement generates a charge pressurep_(charge)>p_(atm) in the intake system. In a third method step, theclosing time t_(intake,closing,2) is calculated by adding the baseclosing time, the additive closing time, and the closing timeretardation, ast_(intake,closing,2)=t_(intake,closing,base,2)+Δt_(intake,closing,2).

Additionally, knock risk may be accounted for as shown in FIG. 5, whichincludes a third branch in the determination of the closing time of thesecond inlet valve as shown in FIG. 4. If there is a risk of knocking,the knock regulator of the internal combustion engine outputs anignition retardation Δ_(ignition) by which the ignition is to beretarded in order that knocking combustion may be reliably prevented.

Then, using the present engine speed n_(mot) and the ignitionretardation Δ_(ignition) output by the knock regulator, a closing timeretardation Δt_(intake,closing,knock) is determined by which the closureof the second inlet valve is to be retarded for the purpose of reducingthe effective compression ratio (upper branch). In this case, theignition retardation Δ_(ignition) which serves as input signal, ispassed through a low-pass filter 1 and a delay element 2 (1/z). Thismakes allowance for the different response behaviors of an ignitionadjustment and of a variable valve drive. For the adjustment of thevalve drive, sufficient time should be available in order that theclosing time of the second inlet valve can be adjusted. The delayensures that the knock regulator, owing to the adjustment of the closingtime of the second inlet valve, regards the originally intended ignitionretardation Δ_(ignition) as being no longer necessary. This results inhigher efficiency.

A closing time retardation Δt_(intake,closing,knock) which is determinedfor the purposes of preventing knocking and by which the closure of thesecond inlet valve is to be retarded must then additionally be takeninto consideration, that is to say added, in the calculation of theclosing time t_(intake,closing,2) (upper branch).

The closing time t_(intake,closing,2) is calculated by adding the baseclosing time, the additive closing time, and the closing timeretardation, ast_(intake,closing,2)=t_(intake,closing,base,2)+Δt_(intake,closing,2)+Δt_(intake,closing,knock).

Turning now to FIG. 6, an example method 600 may be executed by anengine controller (e.g., controller 120) via instructions stored innon-transitory memory for determining the closing time of a second inletvalve in order to control the offset timing between the opening of afirst inlet valve and the closing of the second inlet valve, forexample.

At 602, the method may determine the engine operating conditions. Theengine operating conditions may include, for example, ambienttemperature and pressure, engine speed, intake pressure, spark retard,etc. The operating conditions may be measured and/or estimated.

At 604, the method may determine a base closing timet_(intake,closing,base,2) for the second inlet valve based on thedetermine engine operating conditions determined at 502 and a desiredintake pressure. For example, the base closing time may be determinedbased on a function of desired intake pressure and actual engine speed.The desired intake pressure may be determined via a lookup table, forexample, wherein the table contains setpoints to optimize for hightorque and quick response. In this way, optimal values may be determinedwhile the engine is naturally aspirated, such as when the throttle opensbut before turbocharging occurs, as can be seen in FIG. 3 between 0 and0.5 seconds, for example.

At 606, the method may determine whether charge pressure is greater thanambient pressure. Charge pressure may be determined by subtractingambient pressure from the actual intake pressure. Thus, action 606 maydetermine when a turbocharger, such as turbocharger 190, starts to buildup boost pressure such that Δp_(charge)>0.

If yes at 606, the method may proceed to action 608, wherein additiveclosing time is determined based on the charge pressure. For example,the additive closing time may be determined by the charge pressure e.g.,the actual intake pressure above the ambient pressure, and the actualengine speed. Thus, action 608 may be a correction in the timing of thesecond inlet valve to account for turbocharging. If no at 606, themethod may proceed to action 620.

At 610, the method may determine whether condition for knock is present.For example, it may be determined whether air charge temperature isgreater than a threshold temperature. The engine may be knock-limiteddue to higher ambient temperatures or because of a low octane fuel, forexample, which may increase the air charge temperature.

If no at 610, the method may determine at 614 the closing time of thesecond inlet valve which is the addition of the base intake closing timedetermined at 604 and the additive closing time determined at 608. Themethod may then proceed to action 620.

If yes at 610, the method may determine at 616 a closing timeretardation based on an ignition retardation output from a knockregulator and a present engine speed. For example, an average of thecylinder individual spark retard from the knock control may be filteredand then used as an input with engine speed to determine a closing timeretardation of the second inlet valve. Further, the ignition retardationoutput may additionally be passed through a delay element, such as delayelement 2 of FIG. 5. The delay element may allow for reducingretardation of ignition time, thus reducing its associated efficiencylosses.

At 618, the method may determine closing time of the second inlet valve.The closing time may be determined byt_(intake,closing,base,2)+Δt_(intake,closing,2)+Δt_(intake,closing,knock).Thus, the closing time of the second inlet valve may be corrected forturbocharging and knock limitations.

At 620, the method may include adjusting intake cam position based onthe determined closing time. For example, based on the determinedclosing time, an engine controller may have instructions stored innon-transitory memory to adjust the position of the cams to retard theclosing time of the second inlet valve and/or advance the opening timeof the first intake valve. The intake valves may be actuated to lengthenthe time between the opening of a first inlet valve, e.g., inlet valveI1 of FIG. 2, and the closing of a second inlet valve, e.g., inlet valveI2. For example, at least the second inlet valve may be closed later andafter bottom dead center. In another example, the controller may adjusta cam actuation system, such as cam actuation system 51, based on thedetermined closing time in order to actuate the intake valves via camson a cam-in-cam system.

In this way, the method may optimize efficiency in different loadconditions for a turbocharged direct injection internal combustion, forexample, and may account for more robust knock control withoutsacrificing the efficiency associated with retarding ignition time. Forexample, the method may optimize the shift of a second cam to actuate asecond inlet valve in relation to a first cam at steady state conditionsand at transient conditions, such as when the load shifts from low tohigh.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory. The specific routinesdescribed herein may represent one or more of any number of processingstrategies such as event-driven, interrupt-driven, multi-tasking,multi-threading, and the like. As such, various actions, operations,and/or functions illustrated may be performed in the sequenceillustrated, in parallel, or in some cases omitted. Likewise, the orderof processing is not necessarily required to achieve the features andadvantages of the example embodiments described herein, but is providedfor ease of illustration and description. One or more of the illustratedactions, operations and/or functions may be repeatedly performeddepending on the particular strategy being used. Further, the describedactions, operations and/or functions may graphically represent code tobe programmed into non-transitory memory of the computer readablestorage medium in the engine control system.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, and other engine types. The subject matter ofthe present disclosure includes all novel and non-obvious combinationsand sub-combinations of the various systems and configurations, andother features, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

1. A supercharged applied-ignition internal combustion enginecomprising: at least one cylinder head with at least one cylinder, eachcylinder having at least two inlet openings for the supply of charge airvia an intake system and at least one outlet opening for the dischargeof the exhaust gases via an exhaust-gas discharge system; at least onethrottle flap which is arranged in the intake system; and at least oneexhaust-gas turbocharger is provided, each exhaust-gas turbochargercomprising a turbine arranged in the exhaust-gas discharge system and acompressor arranged in the intake system; a knock regulator which, asoutput signal, provides an ignition retardation Δignition required forthe prevention of knocking, and at least two at least partially variablevalve drives, the valve drives having at least two valves which aremovable between a valve closed position and a valve open position toopen up and block the at least two inlet openings of the at least onecylinder, having valve spring means for preloading the valves in thedirection of the valve closed position, and having at least twoactuating devices for opening the valves counter to the preload force ofthe valve spring means, each actuating device comprising a cam which isarranged on a camshaft and which, as the camshaft rotates, is broughtinto engagement with at least one cam follower element, whereby theassociated valve is actuated, and the cams of the at least two actuatingdevices of the at least two at least partially variable valve drivesbeing rotatable relative to one another; and wherein the at least twovalves are actuated based on a desired manifold pressure and acorrective factor based on a boost pressure.
 2. The superchargedapplied-ignition internal combustion engine as claimed in claim 1,wherein the cams are arranged on an at least two-part camshaft whichcomprises at least two camshaft sections that are rotatable relative toone another, wherein at least one cam is arranged on a first camshaftsection and at least one cam is arranged on a second camshaft section.3. The supercharged applied-ignition internal combustion engine asclaimed in claim 2, wherein the at least two-part camshaft comprises, asfirst camshaft section, a hollow shaft and, as second camshaft section,a shaft arranged rotatably in the hollow shaft and wherein the cams havethe same contour.
 4. The supercharged applied-ignition internalcombustion engine as claimed in claim 1, wherein each cylinder isequipped with a direct-injection means for fuel supply purposes.
 5. Thesupercharged applied-ignition internal combustion engine as claimed inclaim 1, wherein each cylinder has a geometric compression ratioε_(geo)≧11.
 6. The supercharged applied-ignition internal combustionengine as claimed in claim 1, wherein each cylinder has a geometriccompression ratio ε_(geo)≧11.5.
 7. The supercharged applied-ignitioninternal combustion engine as claimed in claim 1, wherein each cylinderhas two inlet openings for the supply of charge air via the intakesystem, and each piston belonging to a cylinder oscillates between a topdead center and a bottom dead center, wherein, when there is a risk ofknocking, at least the second inlet valve is closed later and afterbottom dead center.
 8. The supercharged applied-ignition internalcombustion engine as claimed in claim 7, wherein a closing timeretardation Δt_(intake,closing,knock) by which the closure of the secondinlet valve is to be retarded is determined using a present engine speedn_(mot) and an ignition retardation Δ_(ignition) output by the knockregulator.
 9. A method for operating a supercharged applied-ignitioninternal combustion engine, comprising: actuating a first inlet valveand a second inlet valve of each cylinder of the engine by rotationallyoffsetting cams respectively coupled to the first inlet valve and thesecond inlet valve thereby forming a control offset Δ; actuating thefirst inlet valve earlier than the second inlet valve at a relativelylow load demand; opening a throttle flap and reducing the control offsetΔ by actuating the second inlet valve earlier at an abruptly increasingload demand; increasing the control offset Δ dependent on a chargepressure generated in an intake system by exhaust-gas turbocharging byactuating the second inlet valve later.
 10. The method as claimed inclaim 9, wherein the throttle flap is opened fully in the presence ofthe abruptly increased load demand.
 11. The method as claimed in claim9, wherein the control offset Δ is additionally reduced by actuating thefirst inlet valve later.
 12. The method as claimed in claim 11, in whicheach piston belonging to each cylinder oscillates between a top deadcenter and a bottom dead center, wherein in the presence of therelatively low load demand before the abruptly increasing load demand,the first inlet valve is closed before bottom dead center and the secondinlet valve is closed after bottom dead center.
 13. The method asclaimed in claim 12, wherein the control offset Δ is reduced by thesecond inlet valve being closed before bottom dead center.
 14. Themethod as claimed in of claim 11, further comprising calculating aclosing time t_(intake,closing,2) at which the second inlet valve isclosed by, determining a base closing time t_(intake,closing,base,2)using a present engine speed n_(mot) and a present desired value for apressure p_(intake,des) in an intake system; determining an additiveclosing time Δt_(intake,closing,2) using a present engine speed n_(mot)and a present actual value for a pressure p_(intake) in the intakesystem; and calculating the closing time t_(intake,closing,2) by addingthe base closing time and the additive closing time, wheret_(intake,closing,2)=t_(intake,closing,base,2)+Δt_(intake,closing,2).15. The method as claimed in claim 14, wherein, a predefined ambientpressure p_(atm) is used as a maximum admissible desired value for thepressure p_(intake,des) in the intake system and by means of which thedesired value for the pressure p_(intake,des) in the intake system inthe determination of the base closing time is limited.
 16. The method asclaimed in claim 15, wherein a predefined ambient pressure p_(atm) issubtracted from the present actual value for the pressure p_(intake) inthe intake system in order to determine a charge pressure differenceΔp_(charge), the additive closing time Δt_(intake,closing,2) beingdetermined using said charge pressure difference Δp_(charge) ifΔp_(charge)>0.
 17. The method as claimed in claim 14, further comprisingadjusting the closing time t_(intake,closing,2) by a filtered averagecylinder individual spark retard from a knock control and the presentengine speed n_(mot), to obtain a closing time retardationΔt_(intake,closing,knock) wheret_(intake,closing,2)=t_(intake,closing,base,2)+Δt_(intake,closing,2)+t_(intake,closing,knock).18. A method, comprising: actuating a second inlet valve of a cylinderduring a high load condition such that a time between an opening of afirst inlet valve of the cylinder and a closing of the second inletvalve is lengthened in response to a positive charge pressure.
 19. Themethod as claimed in claim 18, further comprising retarding the closingof the second inlet valve in response to the positive charge pressure.20. The method as claimed in claim 18, further comprising retarding theclosing of the second inlet valve in response to a knock regulatoroutput.